copy: rework copy_file_atomic() to copy the specified file via O_TMPFILE if possible

master
Lennart Poettering 5 years ago
parent 3f40303993
commit ec6bdf7259
  1. 4
      TODO
  2. 48
      src/basic/copy.c
  3. 21
      src/test/test-copy.c

@ -14,6 +14,8 @@ Janitorial Clean-ups:
* Rearrange tests so that the various test-xyz.c match a specific src/basic/xyz.c again
* copy.c: set the right chattrs before copying files and others after
* rework mount.c and swap.c to follow proper state enumeration/deserialization
semantics, like we do for device.c now
@ -25,8 +27,6 @@ Features:
* Add OnTimezoneChange= and OnTimeChange= stanzas to .timer units in order to
schedule events based on time and timezone changes.
* add O_TMPFILE support to copy_file_atomic()
* nspawn: greater control over selinux label?
* cgroups: figure out if we can somehow communicate in a cleaner way whether a

@ -681,31 +681,55 @@ int copy_file(const char *from, const char *to, int flags, mode_t mode, unsigned
}
int copy_file_atomic(const char *from, const char *to, mode_t mode, unsigned chattr_flags, CopyFlags copy_flags) {
_cleanup_free_ char *t = NULL;
_cleanup_(unlink_and_freep) char *t = NULL;
_cleanup_close_ int fdt = -1;
int r;
assert(from);
assert(to);
r = tempfn_random(to, NULL, &t);
if (r < 0)
return r;
/* We try to use O_TMPFILE here to create the file if we can. Note that that only works if COPY_REPLACE is not
* set though as we need to use linkat() for linking the O_TMPFILE file into the file system but that system
* call can't replace existing files. Hence, if COPY_REPLACE is set we create a temporary name in the file
* system right-away and unconditionally which we then can renameat() to the right name after we completed
* writing it. */
if (copy_flags & COPY_REPLACE) {
r = tempfn_random(to, NULL, &t);
if (r < 0)
return r;
fdt = open(t, O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY|O_WRONLY|O_CLOEXEC, 0600);
if (fdt < 0) {
t = mfree(t);
return -errno;
}
} else {
fdt = open_tmpfile_linkable(to, O_WRONLY|O_CLOEXEC, &t);
if (fdt < 0)
return fdt;
}
r = copy_file(from, t, O_NOFOLLOW|O_EXCL, mode, chattr_flags, copy_flags);
if (chattr_flags != 0)
(void) chattr_fd(fdt, chattr_flags, (unsigned) -1);
r = copy_file_fd(from, fdt, copy_flags);
if (r < 0)
return r;
if (fchmod(fdt, mode) < 0)
return -errno;
if (copy_flags & COPY_REPLACE) {
r = renameat(AT_FDCWD, t, AT_FDCWD, to);
if (renameat(AT_FDCWD, t, AT_FDCWD, to) < 0)
return -errno;
} else {
r = link_tmpfile(fdt, t, to);
if (r < 0)
r = -errno;
} else
r = rename_noreplace(AT_FDCWD, t, AT_FDCWD, to);
if (r < 0) {
(void) unlink(t);
return r;
return r;
}
t = mfree(t);
return 0;
}

@ -240,7 +240,27 @@ static void test_copy_bytes_regular_file(const char *src, bool try_reflink, uint
unlink(fn3);
}
static void test_copy_atomic(void) {
_cleanup_(rm_rf_physical_and_freep) char *p = NULL;
const char *q;
int r;
assert_se(mkdtemp_malloc(NULL, &p) >= 0);
q = strjoina(p, "/fstab");
r = copy_file_atomic("/etc/fstab", q, 0644, 0, COPY_REFLINK);
if (r == -ENOENT)
return;
assert_se(copy_file_atomic("/etc/fstab", q, 0644, 0, COPY_REFLINK) == -EEXIST);
assert_se(copy_file_atomic("/etc/fstab", q, 0644, 0, COPY_REPLACE) >= 0);
}
int main(int argc, char *argv[]) {
log_set_max_level(LOG_DEBUG);
test_copy_file();
test_copy_file_fd();
test_copy_tree();
@ -251,6 +271,7 @@ int main(int argc, char *argv[]) {
test_copy_bytes_regular_file(argv[0], true, 1000);
test_copy_bytes_regular_file(argv[0], false, 32000); /* larger than copy buffer size */
test_copy_bytes_regular_file(argv[0], true, 32000);
test_copy_atomic();
return 0;
}

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